Nature of Environmental Health Hazards

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Nature of Environmental Health Hazards

• Didi Supardi, dr.
• Dept. of Public Health Preventive Medicine

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OBJECTIVE

• To describe the difference between hazard risk
• To explain the logic of the various methods of
  classifying environmental hazards
• To describe a scheme for identifying the level of
  hazard toxicity
• To explain why knowledge of the toxicology,
  microbiology, or physical properties of an
  environmental hazard is essential to determining
  the most appropriate approach to its risk
  assessment
• To identify different experimental investigative
  methods
• To explain the biological significance of
  bio-transformation process
• To list the basic characteristics of chemical,
  physical, biological, mechanical, psychosocial
  hazards

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? Required Reading ?

• Yassi A, Kjellström T, de Kok T, Guidotti TL.
  Basic Environmental Health. Chapter 2 Nature of
  Environmental Health Hazards. New York Oxford
  University Press, 2001

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Definition

• Hazard
• a factor or exposure that may adversely affect
  health (Last, 1995)
• a source of danger
• a qualitative term expressing the potential of
  an environmental agent to harm the health of
  certain individuals if the exposure level is high
  enough /or if other conditions apply

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Definition (contd)

• Risk
• the probability that an event will occur, e.g.
  that an individual will become ill or die within
  a stated period of time or before a given age
  the probability of a (generally) unfavorable
  outcome (Last, 1995)
• ? the quantitative probability that a health
  effect will occur after an individual has been
  exposed to a specified amount of a hazard

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Types of EH Hazards

• Biological hazards
• e.g. bacteria, viruses, parasites
• Chemical hazards
• e.g. toxic metals, air pollutants, solvents,
  pesticides
• Physical hazards
• e.g. radiation, temperature, noise
• Mechanical hazards
• e.g. motor vehicle, sports, home, agriculture,
  workplace injury hazards
• Psychosocial hazards
• e.g. stress, lifestyle disruption, workplace
  discrimination, effects of social change,
  marginalization, unemployment

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Types of EH Hazards (contd)

• Classified according to
• nature
• natural vs anthropogenic
• traditional vs modern
• route of exposure
• setting

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• Traditional Hazards
• Disease vectors
• Infectious agents
• Inadequate housing shelter
• Poor-quality drinking water sanitation
• Indoor air pollution from cooking
• Dietary deficiencies
• Hazards of child birth
• Wildlife domestic animals
• Injury hazards in agriculture

• Modern Hazards
• Tobacco smoking
• Transport hazards
• Pollution from sewage industry
• Outdoor air pollution from industry motorcars
• Overuse or misuse of chemicals
• Industrial machinery
• Unbalanced diet

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Biological, chemical physical hazards by
routes of exposure
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BIOLOGICAL HAZARDS

• Include all of the forms of life (as well as the
  nonliving products they produce)
• plants, insects, rodents, other animals, fungi,
  bacterial, viruses, protozoa, a wide variety of
  toxins allergens prion
• Routes of exposure
• Air
• Water
• Food
• Direct penetration
• Biting
• Person exposed ? the agent distributed via
  blood, lymph, or other body fluids to the parts
  of the body most favorable for it to grow

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• Prions (proteinaceous infectious particles)
• Infectious agents (not organisms) made of protein
  (yet to be fully characterized)
• Multiply by converting normal protein molecules
  into dangerous ones by changing their shapes
• Responsible for the various forms of spongiform
  encephalopathy, e.g.
• - bovine spongiform encephalopathy (BSE) or
  mad-cow disease)
• - Creutzfeldt-Jakob disease (CJD)
• - kuru (transmitted by ritual handling of
  bodies brains of the dead)
• Symptoms of the human prion diseases dementia,
  loss of coordination

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• Viruses
• a piece of nucleic acid (either DNA or RNA),
  which makes its progeny by orchestrating the
  production of virus particles by a cell
• viruses that lack a lipoprotein envelope (e.g.
  hepatitis A, gastroenteritis viruses) can grow in
  the human gut be spread by food water
• viruses with a lipoprotein envelope have limited
  survival outside a host so are spread in
  aerosols or inoculations of body fluids from
  person to person (e.g. measles)
• reproduces only inside a host cell
• viral diseases do not respond to antibiotics, but
  some respond to specific antivirals

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• Bacteria
• most have sufficient energy supply to reproduce
  outside a cell
• have genetic material but no nucleus
• divide by splitting in half
• exist singly or in short chains of two or more
• classified by shape, oxygen requirement ability
  to take up a special stain

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• Fungi
• simple plant plant organisms that lack the
  chlorophyll needed to use carbon dioxide
  sunlight to build sugars structural molecules
• classified into yeast (single-celled) or moulds,
  which grow as branching filaments called hyphae
• yeast reproduce by budding, moulds by branching
  longitudinal growth of hyphae, as well as by
  producing sexual spores

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• Protozoa
• the simplest class of animal consisting of a
  single nucleated cell
• each cells has organelles that carry on such
  functions as locomotion, nutrition, excretion,
  respiration
• e.g. plasmodium, cryptosporidium, giardia
• Arthropods
• the large phylum of animal life that includes
  insects, spiders, mites ticks (as well as crabs
  lobsters)
• some of these creatures bite, sting, cause
  allergic reactions, and may serve as vectors for
  viruses other infectious agents

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Growth of biological agents are slowed down or
stopped by

• defense mechanisms of the body
• drugs

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CHEMICAL HAZARDS

• Inorganic Substances
• halogens (e.g. fluorine, chlorine, bromine,
  iodine)
• alkaline compounds (e.g. NH3, Ca(OH)2, KOH, NaOH
• ozone (O3)
• NOx and SOx
• metals (e.g. cadmium, chromium, copper, lead,
  manganese, mercury, nickel, arsenic)

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• Organic Compounds
• aliphatic hydrocarbons (e.g. methane, ethane,
  propane, butane, pentane, hexane, heptane,
  octane)
• alicyclic hydrocarbons (e.g. cyclohexane,
  methylcyclohexane, turpentine)
• aromatic hydrocarbons (e.g. benzene, toluene,
  styrene, naphthalene)
• halogenated hydrocarbons (e.g. chloromethane,
  dichloromethane, chloroform, carbon
  tetrachloride, trichloroethyene, polyviyl
  chloride)
• alcohols (e.g. methanol, ethanol, propanol)

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Route of exposures

• Source
• natural events
• man-made industrial, agricultural, commercial,
  domestic, manufacturing wastes
• Exposure
• inhalation - breastfeeding
• oral ingestion - placental transfer
• absorption via the skin - inoculation direct
  penetration
• absorption via the eyes

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Air, water, dirt, etc
Food, water, drugs
Air
Exposure Media
inhalation
exhalation
ingestion
Major uptake pathways
Skin
Respiratory tract
GI-tract
bile
exfoliation
Blood
Transport distribution
Other organs
Liver
Kidney
Major excretory pathways
Sweat
Hair
Urine
Faeces
external contamination
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Biotransformation

• Hydrophobic or lipophilic ? hydrophilic
• Phase I - the molecule is altered by the
  introduction of electrostatically charged (polar)
  groups
• - result of oxidation, reduction, or hydrolysis
• Phase II substances are combined w/ hydrophilic
  endogenous compounds

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Bioactivation of Benzene
Phase II
Phase I
Benzene (the original chemical)
Phenylglucuronide (hydrophilic easily excreted)
Benzene epoxide (a dangerously toxic product)
Phenol (an intermediate that the body can handle)
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xenobiotics
highly lipophilic metabolically stable
lipophilic
polar
hydrophilic
accumulation in body fat
phase I (bioactivation or inactivation) oxidation,
reduction, hydrolysis
polar
phase II (bioinactivation) conjugation
hydrophilic
extracellular mobilization
plasma circulation
biliary excretion
renal excretion
secretion
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Toxicityany harmful effect of a chemical or a
drug on a target organ

• Systemic toxicity
• Liver toxicity
• Kidney toxicity
• Skin toxicity
• Neurotoxicity
• Immunotoxicity

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• Alteration of genetic
• codes information
• gene mutation
• chromosomal alteration
• gene rearrangements

Biological agents
Chemical agents
DNA
Physical agents

• Gene mutation
• the result of single or multiple base pair
  changes (substitutions, deletions, insertions)
• in the DNA. Normally, the cell defense
  mechanisms can repair DNA damages, recreating
• the original structures. Repair can be faulty,
  leading to heritable changes
• Chromosomal alterations
• via damage by genotoxic agents, leading to
  structural aberrations (breaks, deletions,
  translocations),
• via loss or gain of one or more chromosomes
  sometimes changes in the number of chromosomes
• Gene rearrangements
• characterized by altered gene expression (gene
  amplification, loss of activity). The underlying
  causes
• might be translocations or inversions of large
  parts of chromosomes

Multistage process of carcinogenesis
Initiation
Promotion
Progression
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Toxicity Testing

• Acute toxicity studies
• to predict human effects of short-term,
  high-level exposures can provide a measure of
  the toxic potential of different compounds
• ED50 dose that would cause the effect in half
  of the test population
• LD50 dose that would kill half of the test
  population
• LC50 concentration of gas or vapor that kills
  half the test population
• LD50 LC50 crude indices of toxicity
• Sub-chronic tests
• animals exposed repeatedly to a given chemical
  over a relatively long period (28 days or
  longer), normally 10 of the lifetime of the
  selected animals
• Chronic toxicity testing
• performed by exposing animals to the chemical
  being tested for the whole of the animals
  lifetime
• Reproductive studies
• on parents offspring

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Toxicity Testing (contd)

• Genotoxic short-term tests
• short-term tests for gene mutation chromosome
  alterations both in vitro in vivo
• Human studies
• clinical or epidemiological studies
• Structure-activity relationships

Right-to-know legislation ? hazard identification
control
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PHYSICAL HAZARDS
Forms of potentially harmful energy in the
environment that can result in either immediate
or gradually acquired damage when transferred in
sufficient quantities to exposed
individuals e.g. sound waves, radiation, light
energy, thermal energy, electrical energy
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Noise

• Noise an unwanted sound
• Sound intensity measured in decibels (dB)
• Risk of incurring hearing loss begins w/
  prolonged exposure to sound of 75 dB(A)
• Rule of thumb
• if a loud voice is not understandable at a
  distance of 1 m b/c of excessive background
  noise, the background noise level is above 85 dB
  likely to be dangerous

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Hearing conservation program

• Regular monitoring of the workplace
• Baseline annual audiograms (for all exposed
  workers)
• In-service pre-service (worker) education
• Systematic record keeping
• Worker notification
• Provision of hearing protection

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Other physical hazardsvibration, radiation,
light, lasers, pressure, temperatures
What are potential health effects of such hazards?
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Mechanical Hazards

• those posed by the transfer of mechanical or
  kinetic energy (the energy of motion)
• Injury, trauma, accidents
• Vulnerable groups
• children, the elderly, disadvantaged groups

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The Haddon Matrix
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Psychosocial Hazards

• Potential sources of work-related psychosocial
  stress
• factors intrinsic to the job
• the role of the worker in the organization
• career development
• interpersonal relationships at work
• organizational structure climate

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Thank you